Process of making benzanthrone



Patented Feb. 3, 1931 V UNITED STATES PATENT OFFICE.

IVAN GUBELMANN, ROBERT J'. GOODRICH, AND EDWARD T. HOWELL, OF SOUTH MIL- .WAUKEE, WISCONSIN, ASSIGNORS, BY MEEENE ASSIGNMENTS, TO NEWPORT CHEMI- CAL CORPORATION, A CORPORATION OF DELAWARE PROCESS OF MAKING BENZANTHRONE No Drawing.

This invention relates to a process for the preparation of benzanthrone or a benzanthrone derivative, and more particularly to the reduction of an anthraquinone body to an anthranol body in sulfuric acid and the subsequent condensation of the anthranol body with glycerol to form the corresponding benzanthrone body.

In the processes, heretofore known, for producing benzanthrone similar to the general procedure as outlined above, there are certain objectionable features which are believed to have been satisfactorily overcome in the present invention. Former known processes have recommended for the reduction step of anthraquinone to anthranol, reducing z'fgents such as aluminum, aluminum bronze, freshly'precipitated copper, aniline sulfate, and the like. Some of the known methods result in comparatively lower yields attended by comparatively higherraw material cost than in the case of our present invention.

It has likewise recently been disclosed that inthe general reactions, especially the condensation step wherein the anthranol is reacted upon with glycerol to form benzanthrone, the temperature must be very accurately controlled, particularly with regard to the maximum temperature at the end, to avoid serious detrimental results. It has fur-- thermore been'found that the use of a single metal as reducing agent is at times accompanied by violent and almost uncontrollable reaction speed and as a consequence gassing results, with a resulting loss in efficiency in the use of the reducing agent and with a diminution in the yield of benzanthrone;

It is therefore an object of this invention to provide a method for the preparation of a benzanthrone body which will overcome to a large degree the objectionable features as outlined above, resulting in a final product of high purity and in higher yields than have previously been disclosed.

It is a further object of this invention to provide a method of minimizing the amount of gassing. during the reduction step in order to obtain .a more efficient use of the reducing agent and to provide a method which is not so extremely sensitive to maximum temper- Application filed February 6, 1928. Serial No. 252,422.

atures, whereby a more flexible process as regards temperature control results, and a more complete condensation to benzanthrone made possible.

Other and further important objects of this invention will become apparent from the following description and appended claims.

In general, the improved process contemplates the reduction of an anthraquinone body to an anthranol body by the use of a reducing agent substantially as follows. A copper salt solution, such as a solution of copper sulphate, copper acetate or other suitable copper salts, is added to the solution of the anthraquinone in sulfuric acid. In this connection it will, of course, be understood that copper sulfate may alternatively be formed as such in this solution by the addition of copper to the sulfuric acid. To this mixture containing the copper salt is added a finely divided metal such as zinc, aluminum or the like. The metal added is'only limited to the extent that it must be capable of displacing copper from solution. Suitable metals can readily be determined by consulting a table of a series of the metals arranged in the order of their respective electromotive forces.

By using this method of reduction highly satisfactory results are obtained. The exact mechanism of the reaction is not known, but it isbe'lieved that the copper is present in solution in a nascent state, probably as a nascent copper compound, which while nascent acts as the reducing agent. This appears to be the case, since no precipitation of copper metal has ever been observed. Probably, therefore, the copper formed in the nascent state is used up as fast as produced. The formation of the copper compound in a nascent state is believed to be the result of the action upon the copper salt in solution of nascent, hydrogen, generated by the metals added, such as zinc, aluminum and the like. Obviously the nascent hydro gen may be formed insolution otherwise than by the addition of finely divided metals to the solution, as for instance, electrolytically. Notwithstanding the hypothetical nature of the theory of the reaction, our improved I.

water.

method appears to furnish the most economically practical method known to us for the production of benzanthrone.

Without limiting our invention to any particular procedure, the following examples, in which parts by weight are given, will serve to illustrate our method in its preferred forms.

Example I To 10 parts of anthraquinone in 157 parts of sulfuric acid (monohydrate) is added a solution of 5.85 parts of copper sulfate (crystals) in 35 parts of water. This mixture, which is now about sulfuric acid concentration, is cooled to 28 to 30 C. There are then added 10 parts of glycerol in 6 parts of water and at a temperature of 28 to 30 (3., over a period of about 1 hour, L63 parts of finely divided zinc dust. The reduction mixture is stirred for about two hours at 25 to 30 (1, heated to 120 to 125 C. over a pe riod of one hour and held while agitating, at 120 to 125 C. for an additional hour. The mass is then poured into 1570 parts of hot The diluted mass is filtered and the filter cake washed with a small amount of water until practically acid free.

The benzanthrone thus obtained may be further purified by hot extraction with 1% sodium carbonate solution until all soluble parts are removed and then washed with water. The yield of purified material thus obtained is substantially equal to that theoretically expected. The final product melts at about 170 C.

Example [I 10.85 parts of o-benzoyl benzoic acid are added with stirring to 157 parts of fuming sulfuric acid containing 10% free SO This solution is heated at to C. until anthraquinone formation is complete. The condensation mass is now cooled and a solution of 5.85 parts of copper sulfate crystals in 35 parts of water added, with further cooling, over a period of about one hour. 4.63 parts of zinc dust are now added gradually over a period of one hour at 28 to 30 C. and the reduction mixture stirred for 2 hours at 30 C. There is then slowly added a solution of 10 parts of glycerol in 6 parts water at 25 to 30 (1, and the mass heated to to C. during a period of one hour and held at 120 to 125 C. with agitation for an additional hour. The reaction mixture is worked up as above, giving a product practically identical in yield and quality with that of Example 1.

Example [II 1.63 parts of finely divided aluminum are used in place of 4.63 parts of zinc dust, as in Example H, and the procedure carried out otherwise as in Example 11.

Example IV ture of about. 30 C. there is then added 4A5 parts of zinc dust over a period of 1 hour. The mixture is then held at 30 0. for two hours and heated to 120 C. over a period of an hour. it is agitated 120 to C. for one hour, then cooled and added to 1330 parts of cold water. The dilution mass is cooled to room temperature, filtered and the filter cake washed until practically acid free. The cake is then washed with a 1% solution of caustic soda until the wash waters are clear and then washed with water until alkali free. The product is methyl benzanthrone.

We are aware that numerous details of the process may be varied through a wide range Without departing from the principles of this invention, and we, therefore, do not purpose limiting the patent granted hereon otherwise than necessitated by the prior art.

We claim as our invention:

1. In the process of making anthraquinone derivatives, the step of reacting upon an anthraquinone body in concentrated sulfuric acid with a copper salt and a metal higher than copper in the electromotive series to produce an anthranol body.

2. In the process of making anthraquinone derivatives, the step which comprises reacting upon an anthraquinone body in concentrated sulfuric acid with copper sulfate and zinc dust to produce an anthranol body.

3. In the process of making an anthraquinone derivative, the step of reacting upon anthraquinone in concentrated sulfuric acid with a copper salt and a metal higher than copper in the electromotive series to produce anthranol.

4. In a process of making an anthranol body, the step of reacting with copper sulfate and zinc dust upon a cooled and diluted condensation mass obtained by condensing ortho benzoyl benzoic acid in fuming sulfuric acid.

5. The process of making an anthranol, which comprises reducing anthraquinone in concentrated sulfuric acid with copper sulfate and zinc dust at a temperature of about 25 to 30 C.

6. The process of reducing an anthraquinone body to an anthranol body, which comprises adding a copper salt to an anthraquinone body in concentrated sulfuric acid and then slowly adding finely divided zinc dust to the sulfuric acid mass while maintaining the temperature of the mass at about 25 to 30 C.

7. In a process ofmaking an anthranolbody, the step of reacting with copper sulfate and a metal higher than copper in the electromotive series upon a cooled and diluted condensation mass obtained by condensing ortho-benzoyl benzoic acid in fuming sulfuric acid.

8. The process of making an anthranol, which comprises reducing anthraquinone in cencentrated sulfuric acid with copper sulfate and a metal higher than copper in the electromotive series at a temperature of about 25 to 30 C.

9. The process of reducing an anthraquinone body to an anthranol body, Which comprises adding a copper salt to an anthraquinone body in concentrated sulfuric acid and then slowly adding a finely divided metal higher than copper in the electromotive series to the sulfuric acid mass While maintaining n the gemperature of the mass at about to In testimony whereof We have hereunto subscribed our names at Carrollville, Milwaukee County, Wisconsin.

' IVAN GUBELMANN.

ROBERT J. GOODRIOH. EDWARD T. HOWELL. 

